Fuel burning apparatus



May 28, 1957 E. HUBEL FUEL BURNING APPARATUS Filed June 16, 1955 lv f l1 I ATTORNEY States Patent Oflice 2,793,626 Patented May 28, 1957 FUELBURNING APPARATUS Ernst Hiihel, Oberhausen, Germany, assignor to TheBabcock & Wilcox Company, New York, N. Y., a corporation of New JerseyApplication June 16, 1953, Serial No. 362,024

Claims priority, application Germany June 18, 1952 8 Claims. (Cl.122--235) The present invention relates in general to apparatus forburning ash-containing solid fuels under conditions which result in ahigh output of high temperature gaseous products of combustion,substantially free of entrained slag or ash particles. Moreparticularly, the invention is directed to a structural arrangement offurnace for burning certain varieties of coal which, due to their highcoking characteristics, are preferably maintained in suspensionthroughout the coking stage and thus until the coke particles are nolonger sticky whereupon the particles may be directed into the maincombustion zone for movement along walls thereof at increased velocity.

Accordingly, the invention provides for the combustion of solid fuel insuccessive stages, in successive chambers, with a combustible fuel-airmixture travelling in a helical path through one chamber at relativelylow velocity, and in a continuing helical path through a succeedingchamber at increased velocity. Suitably, the transition from one chamberto the other is effected without substantial change of available flowarea through the connecting passage or passages. For this purpose, thesuccessive chambers are preferably of cylindrical formation and disposedin concentric relation about a common central axis, with fuel andcarrier air being initially admitted to an outer chamber, and theultimate products of combustion discharged from an inner chamber.

In the operation of cyclone furnaces heretofore constructed, a burningfuel-air mixture is caused to travel therethrough at high velocity andthus remains within the furnace for only a very short period. Thus, fora cyclone furnace of prior construction providing a total heat output ofQ:5,000,000 kcal./hr./m. the stay period within the furnace is aboutone-tenth of a second. Although the coarser fuel particles are retainedin the fLlIIlElCt; by the slag film on interior wall surfaces, only apart of the total interior space may be available for active combustion,particularly with coals having strong coking characteristics, due to theprogressive heating of the fuel up to the combustion stage, and thedegasification, whereby the expenditure of energy to provide highvelocities of fuel movement during these preliminary stages ispractically wasted.

However, by providing a separate heat insulated chamber through which anincoming coal-air mixture is caused to move at relatively low velocity,with the fuel particles in suspension, ample time is afforded to enablethe coal particles to be maintained in suspension until such particlesare no longer sticky and the coke skeleton is firm, whereupon thefuel-air stream may be directed into a succeeding chamber, suitably of acyclone type, in which combustion may be completed. As herein disclosed,the fuel inlet chamber is formed as an integral addition to acylindrical cyclone chamber and furthermore is arranged concentricallytherewith to provide an annular surrounding space. Such an arrangementof inlet chamber results in a saving of space and heat and, despite itsspatial restriction, permits variations to be made in its structuralformation especially in respect to features affecting the movement ofcarrier air therethrough.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which I have illustrated and described a specific embodimentof my invention.

Of the drawings:

Fig. l is a vertical section of a cyclone furnace constructed as anembodiment of the invention; and

Fig. 2 is a horizontal section of Fig. 1, taken along line 2--2.

As shown in the drawings, a cyclone furnace A, of cylindrical formationabout a vertical central axis, provides inner and outer chambers B and Cof circular cross section, in concentric arrangement with respect to theaxis. The inner chamber B constitutes a combustion chamber of thecyclone type having an upper portion of its cylindrical defining wall 5conically contracted as at 6 toward a central circular gas outlet 7. Alower portion of wall 5 is similarly contracted at 8 toward a centralcircular slag outlet 9 at the bottom, from which position wall portions10 diverge downwardly toward a slag disposal means, not shown, where aknown form of seal against infiltration of air is effected.

The outer chamber C is of annular formation about an upper portion ofchamber B, with its inner Wall 12 formed in common with portions of wall5 in :a manner hereinafter described, and its outer wall 14 being formedwith an intermediate cylindrical portion 15 concentric with the innercylindrical wall 5. The upper and lower ends of chamber C arerespectively closed by conical upper and lower end wall portions 16 and17, of which the portion 16 is joined at its upper end to the conicalupper end wall portion 6 of chamber B, at the same inclination, and endportion 17 is joined at its lower end to the main cylindrical furnacewall 5.

The outer cylindrical wall 14 of the annular chamber C is formed withcircumferentially spaced inlet ports 13 through which, with the aid ofnozzles 19, a fluent mixture of solid fuel particles suspended in air isdirected into an upper region of chamber C, in approximately tangentialrelation to the inner surface of wall 14. The inner circumferential wall12 of chamber C is formed with circumferentially spaced ports 21 whichopen into the central chamber B from a lower region of chamber Cadjacent its inclined bottom wall 17. The ports 21 are formed withopposing sides 22, 22 which converge inwardly toward chamber B so as todirect the burning fuelair streams tangentially into that chamber, inconformity with the directional movement within chamber C. At anelevation below ports 21, the cylindrical wall 5 of chamber B is formedwith circumferentially spaced inlet ports 23 through which, from nozzles24, secondary air is directed into the central chamber B, inapproximately tangential relation to the inner surface of itscircumferential wall 5.

The entire furnace wall structure is further defined and cooled by meansof tubes 25 through which fluid from an exterior source may becirculated; for example, by including such tubes in the circulatorysystem of an associated fluid heating unit, not shown, suitably in themanner disclosed in U. S. Patent No. 2,594,312.- In the main cylindricalwall 5, below ports 21, the tubes 25 are arranged in a circular row,with suitable intertube spaces at intervals to allow for theinstallation of secondary air inlet nozzles 24. At a lower elevation,certain tubes 25a are bent inwardly, and then outwardly, to define thelower slag outlet 9, whereas other tubes 25b continue downwardly, asindicated, for connection, with tubes 25a, to a fluid supply means, notshown.

From an elevation subjacent ports 21, every fifth tube 25c, throughoutthe circumference of wall 5, is continued upwardly to define the uprightwall portions 20 between successive ports 21. Above the ports 21, anintermediate portion of each tube 250 is formed with several branches25d which, as diagrammatically indicated, define the upper major portionof wall 12, between ports 21 and the conical end wall portion 6. Fromthe same elevation subjacent ports 21, the remaining tubes 25s areextended upwardly within the outer wall 14 of annular chamber C. Thetube lengths 25c and 25a are also included in the annular upper end wallformations 6 and 16 which surround the gas outlet 7. As will beunderstood, all such wall cooling tubes may be arranged with their upperdischarge ends connected to a suitable outlet header means, or the like.

In each of the outer walls, as above described, the tubes 25 anddesignated portions thereof are desirably provided in known manner withwelded-on studs, and with refractory material 26 filling the intertubespaces and covering the tubes on both sides in their respective rows. Agas tight metallic casing 27 is provided for all exterior furnace wallsurfaces.

During operation of the furnace, a solid fuel, such as coal, ofrelatively small particle sizes, is introduced in a stream of primaryair through each of the nozzles 19 which open tangentially into theannular preparation chamber C, suitable provision being made instarting-up for igniting the fuel upon its initial introduction into thechamber. The burning fuel-air streams move in a generally helical pathdownwardly along the outer circumferential wall 14 where, at the bottom,the burning mixture and slag are discharged through ports 21 into thecentral cylindrical chamber B, the slag following the slope of the lowerwall 17 and gravitating toward and through the bottom outlet 9.

The rotational movement of the fuel-air mixture is maintained in chamberB in the same direction, and the combustion of fuel continued andcompleted therein, by the tangential introduction of secondary air athigh velocity through nozzles 24 which are circumferentially spaced intwo rows at an elevation subjacent ports 21. In the course of combustionwithin chamber B, the helical movement of the burning mixture iscontinued along wall in an upward direction, with the gases ofcombustion discharging through the upper central outlet 9, while theslag is deposited in a molten state on adjacent wall areas along whichit flows downwardly toward the bottom outlet 9 through which it isdischarged.

While in accordance with the provisions of the statutes I haveillustrated and described herein a specific form of the invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the apparatus disclosed without departing fromthe spirit of the invention covered by my claims, and that certainfeatures of the invention may sometimes be used to advantage without acorresponding use of other features.

I What is claimed is:

1. A cyclone furnace having walls defining an inner cyclone chamber ofsubstantially circular cross section about an upright axis and an outerfuel inlet chamber of annular formation about said cyclone chamber, saidwalls including a main circumferential wall extending substantiallythroughout the height of said furnace and having a portion common toboth of said chambers, means for introducing a combustible mixture ofash-containing fuel and air into said annular chamber and'elfecting ahelical movement thereof downwardly along the outer circumferential wallof said annular chamber, said common wall portion being formed withcircumferentially spaced openings through which the burning fuel-airmixture is directed laterally into a lower-portion 'ofsaid innerchamber, said outer chamber having a ci'rcuini ferentially continuousbottom end wall joined to said common wall portion at a locationsubjacent said openings, means for introducing secondary air into saidcyclone chamber and effecting a helical movement of the burning mixturetherein toward the upper end of said inner chamber, and a slag outletand a gas outlet discharging respectively from a lower and an upperportion of said cyclone chamber.

2. A cyclone furnace having a main circumferential wall extendingsubstantially throughout the height of said furnace and defining aninner cyclone chamber of substantially circular cross section about anupright axis, an outer circumferential wall defining with said main wallan annular outer chamber having an annular lower end wall of upwardlyconcave conical formation and joined throughout its inner periphery tosaid main wall at an elevation upwardly spaced from the lower end ofsaid furnace, means for introducing air and ash-containing fuel insuspension into an upper portion of said annular chamber and effecting ahelical path of travel thereof downwardly along said outercircumferential wall, said main wall being formed with circumferentiallyspaced openings through which gases and slag from said outer chamber aredischarged into said inner chamber, said openings being arrangedsuperjacent said lower end wall, and nozzle means for introducingsecondary air tangentially into said inner chamber at an elevationsubjacent said openings for continuing and completing combustion of thefuel, said nozzle means being arranged to maintain the same rotationaldirection of movement of fuel and gases within said inner chamber asWithin said annular chamber, said inner chamber having a slag outletformed at its lower end and a gas outlet formed at its upper end.

3. A cyclone furnace having walls defining an inner cyclone chamber ofsubstantially circular cross section about an upright axis and an outerfuel inlet chamber of annular formation about said cyclone chamber, saidwalls including a main circumferential wall having a portion common toboth of said chambers, means for introducing a combustible mixture ofash-containing fuel and air into said annular chamber and effecting ahelical movement thereof downwardly along the outer circumferential wallof said chamber, said common wall portion being formed with openingsthrough which the burning fuelair mixture is directed downwardly intosaid inner chamber, means for introducing secondary air into saidcyclone chamber and effecting a helical movement of the burning mixturetherein toward the upper end of said inner chamber, and a slag outletand a gas outlet discharging respectively from a lower and an upperportion of said cyclone chamber, said annular fuel inlet cham ber beingclosed at the bottom with a conical wall converging downwardly towardsaid main wall and joined thereto directly below said openings, saidfuel inlet chamber being closed at the top with a conical wallconverging upwardly over said inner chamber in the direction of said gasoutlet.

4. A cyclone furnace having walls defining an inner cyclone chamber ofsubstantially circular cross section about an upright axis and an outerfuel inlet chamber of annular formation about said cyclone chamber, saidwalls including a main circumferential wall having a portion common toboth of said chambers, means for introducing a combustible mixture ofash-containing fuel and air into said annular chamber and effecting ahelical movement thereof downwardly along the outer circumferential wallof said chamber, said common wall portion being formed with openingsthrough which the burning fuel-=air mixture is directed downwardly intosaid inner chamber, means for introducing secondary air into saidcyclone chamber and effecting a helical movement of the burning mixturetherein toward the upper end of said inner chamber, and a slag outletand a gas outlet discharging respectively from a lower and an upperportion of said cyclone chamber, said annular fuel inlet chamber isclosed at the bottom with a wall of upwardly concave formation slopingdownwardly and inwardly toward said -main circumferential wall, saidopenings in said common wall portion having inclined bottom surfacesformed as extensions of the sloping upper surface of said bottom wall.

5. A cyclone furnace as defined in claim 4 and further comprising fluidconducting tubes arranged upright within said main circumferential wall,said etubes being disposed in part between said openings through whichgases and slag are discharged from said outer chamber.

6. A cyclone furnace as defined in claim 5 and further comprising othertubes having 'lower portions interspersed with said tubes within saidmain circumferential wall, said other tubes having upper portionsextending within said inclined bottom wall of said annular chamber andcontinuing toward said upper gas outlet.

7. A cyclone furnace having a main circumferential wall defining acyclone chamber of substantially circular cross section about an uprightaxis, an outer circumferential wall defining with said main wall anannular outer chamber having an annular lower end wall of upwardlyconcave conical formation and joined at its inner periphery to said mainwall, means for introducing air and ashcontaining fuel in suspensioninto an upper portion of said annular chamber and effecting a helicalpath of travel thereof downwardly along said outer circumferentialw-a'll, said main wall being [formed with circumferentiallly spacedopenings through which gases and slag from said outer chamber aredischarged into said inner chamber and nozzle means for introducingsecondary air tangentially into said inner chamber at an elevationsubjacent said openings for continuing and completing combustion of thefuel, said nozzle means being arranged to maintain the same rotationdirection of movement of fuel and gases within said inner chamber aswithin said annular chamber, said inner chamber having a slag outletformed at its lower end and a gas outlet formed at its: upper end, saidmain wall including a ciroumferentially continuous upper wall portion atelevations above said spaced openings, said furnace further comprisingfluid conducting tubes arranged upright within said main wall, saidtubes at the elevation of said openings being arranged with single tubelengths disposed in wall portions separating said openings, saidsingletube lengths at the upper ends of said openings being formed withbranches to provide an increased number of fluid conducting tube lengthportions for said circumferential'ly continuous wall portion above saidopenings.

8. A cyclone furnace as defined in claim 7 wherein said walll tubebranches are restored to single tube lengths in wall portions adjacentsaid upper gas outlet.

References Cited in the file of this patent UNITED STATES PATENTS1,180,792 Norrman Apr. 25, 1916 2,625,791 Yellott Jan. 20, 1953 FOREIGNPATENTS 587,240 Great Britain Apr. 18, 1947

